- Three to six includes the Game Master (so two-five player characters). This number is really arbitrary, though - I mostly chose it because that's the size range I'm comfortable running. Unlike something like D&D, where you need to be conscious of how many players you have when planning adventures (especially fights), Under the Neighborhood isn't super concerned with that.
- It really depends on what your skillsets and interests are! For GMs who are really comfortable with prep and numbers but less comfortable with improv, I'd recommend using a pre-made module for a game like D&D. For GMs who enjoy improv storytelling but are less comfortable with numbers/mechanics, PbtA and similar "rules-lite" systems can be great! Using Under the Neighborhood as an example, our most in-depth pre-made Adventure is only 648 words long. It provides 1 NPC, a three-act summary, and less than 200 words outlining battle mechanics. This makes it so that it's really easy to adjust what you're doing based on your players' actions, but it also gives you less concrete numbers/NPCs/etc. to rely on. Personally, I started with something in-between D&D and PbtA (Cypher System), but even after GMing for years, I'd still be uncomfortable GMing with a crunchier game like D&D and Pathfinder, simply because that's not how I like to run things. In the end, I'd recommend doing a one-shot with whatever game you're most interested in playing. The best way to learn what you're most comfortable with is by trying!